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Cutting Edge: Silencing Suppressor of Cytokine Signaling 3 Expression in Dendritic Cells Turns CD28-Ig from Immune Adjuvant to Suppressant¹

Department of Experimental Medicine, University of Perugia, Perugia, Italy

	Abstract

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CTLA-4-Ig and CD28-Ig are both agonist ligands of B7 coreceptor molecules on mouse dendritic cells (DCs), yet they bias the downstream response in opposite directions, and CTLA-4-Ig promotes tolerance, whereas CD28-Ig favors the onset of immunity. Although B7 engagement by either ligand leads to a mixed cytokine response, a dominant IL-6 production in response to CD28-Ig prevents the IFN--driven induction of immunosuppressive tryptophan catabolism mediated by IDO. In the present study, we show that silencing the expression of suppressor of cytokine signaling 3 (SOCS3) in DCs by RNA interference renders CD28-Ig capable of activating IDO, likely as a result of unrestrained IFN- signaling and IFN--like actions of IL-6. Thus, in the absence of SOCS3, CD28-Ig becomes immunosuppressive and mimics the action of CTLA-4-Ig on tryptophan catabolism.

	Introduction

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Suppressor of cytokine signaling (SOCS) ³ proteins have emerged as critical modulators of cytokine-mediated processes (1). Not only does the feedback inhibitor SOCS3 attenuate IL-6 signaling (2) but up-regulation of SOCS3 by IL-6 may be responsible for inhibition of STAT-dependent signaling by IFNs (3). In addition to modulation of IFN--inducible genes, a series of recent studies with various experimental approaches have demonstrated that SOCS3 is involved in the prevention of IFN--like responses in hepatocytes and macrophages stimulated with IL-6 (4, 5, 6). It has been suggested that, in the absence of SOCS3, IL-6 may become immunosuppressive, activating genes typically induced by IFNs (7).

In murine dendritic cells (DCs) treated with the synthetic immunomodulator CTLA-4-Ig, an autocrine IFN- response leads to STAT1-dependent activation of the gene encoding IDO, thus initiating the immunosuppressive pathway of tryptophan catabolism (8, 9, 10). Although CTLA-4-Ig and CD28-Ig bind the same B7-1 and B7-2 receptor molecules, an as yet unclarified divergent pathway in B7 signaling by CD28-Ig leads to early and sustained production of IL-6, whose autocrine effects up-regulate SOCS3 and prevent IDO activation by cosecreted IFN- (11, 12). This raises the possibility that in DCs treated with CD28-Ig in the absence of SOCS3, IFN- signaling may be released from a critical inhibitory control, leading to effective induction of tryptophan catabolism. In addition, IL-6 might contribute to IDO activation by virtue of its ability to trigger IFN--like responses (13). By silencing SOCS3 expression with a specific small interfering RNA (siRNA), in the present study, we provide evidence that CD28-Ig treatment leads to the induction of IDO and the onset of tolerogenic properties in DCs lacking SOCS3. These effects appear to result from a combination of unopposed IFN- signaling and the occurrence of IFN--like actions by IL-6.

	Materials and Methods

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Mice and reagents

Female DBA/2J (H-2^d) mice were obtained from Charles River Breeding Laboratories (Calco). Neutralizing XMG1.2 mAb to IFN- and mAbs 6B4 (anti-mouse IL-6) and 15A7 (anti-mouse IL-6R) were described previously (11). CTLA-4-Ig and CD28-Ig were fusion proteins generated from the extracellular domains of murine CTLA-4 and CD28, respectively, and the Fc portion of a murine IgG3, with native IgG3, or the Fc portion of IgG3 alone (Ig-C3) representing the control treatments (8, 11). The enzyme inhibitor 1-methyl-DL-tryptophan (1-MT) was purchased from Sigma-Aldrich (Milan, Italy). The P815AB (amino acid sequence LPYLGWLVF) peptide was synthesized and purified as described previously (14, 15). All in vivo studies were done in compliance with National and Perugia University Animal Care and Use Committee guidelines.

DC preparations and treatments and immunization

Splenic DCs were purified by MACS using CD11c MicroBeads and MidiMacs (Miltenyi Biotec) in the presence of EDTA to disrupt DC-T cell complexes (14, 15). Cells were >99% CD11c⁺, >99% MHC I-A⁺, >98% B7-2⁺, <0.1% CD3⁺, and appeared to consist of 90–95% CD8^–, 5–10% CD8⁺, and 1–5% B220⁺ cells. Additionally, DC populations were separated into CD8^– and CD8⁺ fractions by means of CD8 MicroBeads (Miltenyi Biotec) (14, 15). The CD8^– fraction was 45% CD4⁺ and typically contained <0.5% contaminating CD8⁺ cells. Less than 1% CD8⁺ and <5% CD8^– DCs expressed the B220 marker, respectively (16). DCs were exposed to 40 µg/ml CTLA-4-Ig, CD28-Ig, IgG3, or Ig-C3 or to 20 ng/ml rIL-6 for 24 h at 37°C in the presence or absence of 2 µM 1-MT (11, 14). For cytokine neutralization, DCs were exposed to fusion proteins in vitro in the presence of 6B4 and 15A7 mAbs (for IL-6 neutralization; each at 10 µg/ml) or anti-mouse IFN- mAb (10 µg/ml) as described previously (11). For immunization, cells were washed between and after incubations before peptide loading (5 µM, 2 h at 37°C), irradiation, and i.v. injection into recipient hosts. A total of 3 x 10⁵ CD8^– (or, where indicated, CD28-Ig-treated CD8⁺) DCs was injected either alone or in combination with 3% CD8⁺ DCs.

siRNA synthesis and transfection

The siRNA sequences specific for murine SOCS3 (sense, 5'-GGAGCAAAAGGGUCAGAGGtt-3'; antisense, 5'-CCUCUGACCCUUUUGCUCCtt-3') were selected, synthesized, and annealed by the manufacturer (Ambion). For transfection, siRNAs (6.7 µg) in 30 µl of transfection buffer (20 mM HEPES and 150 mM NaCl (pH 7.4)) were pipetted into a sterile Eppendorf tube. In a separate polystyrene tube, 6.7 µg of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) were mixed with 30 µl of transfection buffer, and then both solutions were mixed gently by pipetting several times. After incubation at room temperature for 20 min, the mixture was added to 1 ml of complete medium containing 10⁶ DCs and incubated for 24 h at 37°C in the presence or absence of IL-6 or CD28-Ig. Cells were then recovered, washed, and immediately used for in vitro or in vivo experiments. siRNA treatment resulted in complete disappearance of SOCS3 transcripts at 24–48 h. Control treatments consisted of either or both of two different controls: mock-transfected DCs, i.e., cells treated with DOTAP alone (17), and Negative Control siRNA (Ambion). Expression of SOCS3 (sense, 5'-GCCATGGTCACCCACAGCAAGTT-3'; antisense, 5'-AAGTGGAGCATCATACTGATCCAGGA-3') and control SOCS1 (sense, 5'-ATGGTAGCACGCAACCAGG-3'; antisense, 5'-AAGACGAGGACGAGGAGGG-3') transcripts was evaluated by RT-PCR analysis using specific primers.

Skin test assay

A skin test assay was used for measuring class I-restricted delayed-type hypersensitivity responses to synthetic peptides as described previously (11, 17). Results were expressed as the increase in footpad weight of peptide-injected footpads over that of vehicle-injected counterparts. Data are the mean ± SD for at least six mice per group. The statistical analysis was performed using Student’s paired t test by comparing the mean weight of experimental footpads with that of control counterparts. The data reported are representative of at least three independent experiments.

Kynurenine assay

IDO functional activity was measured in vitro in terms of the ability of DCs to metabolize tryptophan to kynurenine, the concentrations of which were measured by HPLC as described previously (8).

Western blot analyses

IDO expression was investigated as previously described using a specific Ab (9). On studying STAT phosphorylation, CD8⁺ DCs were exposed to IL-6 (20 ng/ml) for 10 min. After SDS-PAGE resolution, immunoblotting was performed by sequential exposure to anti-phospho-STAT1/anti-STAT1 or anti-phospho-STAT3/anti-STAT3 Abs, as described previously (17, 18).

	Results and Discussion

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CTLA-4-Ig and CD28-Ig have disparate effects on Ag presentation by DCs

DC populations in the spleens of DBA/2 mice consist of CD8^– (90%) and CD8⁺ (10%) fractions that mediate the respective immunogenic and tolerogenic presentation of the synthetic tumor/self nonapeptide P815AB (19). Upon transfer into recipient hosts, peptide-loaded CD8^– DCs initiate immunity, and CD8⁺ DCs initiate anergy when Ag-specific skin test reactivity is measured at 2 wk after cell transfer (14, 20). In line with previous results of functional plasticity of DC subsets (9, 15), Fig. 1A shows that otherwise immunogenic CD8^– DCs became tolerogenic as a result of DC exposure to CTLA-4-Ig before peptide loading and transfer into recipient mice. The effect of CTLA-4-Ig on CD8^– DCs was contingent upon autocrine IFN- and the expression of functional IDO because it was negated by the presence of either IFN--neutralizing Ab or the enzyme inhibitor 1-MT during DC exposure to CTLA-4-Ig. Consistent with previous results of adjuvant activity by CD28-Ig (11), otherwise tolerogenic CD8⁺ DCs were made capable of immunogenic presentation of P815AB when exposed to CD28-Ig before peptide loading and transfer into recipient hosts, which was dependent on autocrine IL-6 (Fig. 1B). Thus, CTLA-4-Ig and CD28-Ig affect the functional plasticity of DC subsets in opposite directions through the respective dominant actions of autocrine IFN- and IL-6. As in other model systems with CTLA-4-Ig (8, 16, 21), tolerogenesis by CTLA-4-Ig acting on CD8^– DCs requires tryptophan catabolism.

View larger version (20K): [in this window] [in a new window]   FIGURE 1. The default pattern of Ag presentation by DC subsets can be subverted by CTLA-4-Ig or CD28-Ig through the respective induction of IFN- or IL-6. A, CTLA-4-Ig confers suppressive properties on CD8– DCs through mechanisms involving tryptophan catabolism. DCs fractionated according to CD8 expression and pulsed with P815AB were transferred into recipient mice to be assayed for skin test reactivity. The CD8– DC fraction was used as such or after treatment with CTLA-4-Ig or control IgG3. Experimental groups included the use of CD8– DCs treated with neutralizing Ab to IFN- or 2 µM 1-MT during exposure to CTLA-4-Ig. B, CD28-Ig confers IL-6-dependent immunogenic properties on CD8+ DCs. Peptide-pulsed CD8+ DCs were transferred into recipient mice to be assayed for skin test reactivity. Cells were used as such or after treatment with CD28-Ig or control IgG3, in the presence or absence of anti-IL-6 and anti-IL-6R Abs. The skin test assay was performed at 2 wk. *, p < 0.001, experimental vs control footpads.

The default tolerogenic potential of CD8⁺ DCs is such that as few as 3% CD8⁺ DCs admixed with CD8^– DCs will negate the induction of immunity to P815AB by the latter cells upon transfer into recipient hosts (22, 23). However, the effect is no longer observed when the CD8⁺ DC fraction is treated with rIL-6 before peptide loading and mixing with CD8^– DCs (14). We examined whether SOCS3 expression is required for CD28-Ig and IL-6 effects on CD8⁺ DCs. Splenic DCs were fractionated, and specific SOCS3 gene silencing was achieved in the CD8⁺ fraction with siRNA technology (Fig. 2A). P815AB-pulsed CD8^– DCs were injected either alone or in combination with 3% CD8⁺ DCs, either untreated or treated with CD28-Ig or rIL-6, with or without concomitant siRNA-SOCS3 treatment (Fig. 2B). The results showed that SOCS3 was an absolute requirement for the occurrence of regulatory effects by CD28-Ig and rIL-6 on CD8⁺ DCs. Thus, in the absence of SOCS3, CD8⁺ DCs are refractory to immunomodulation by endogenous or externally added IL-6, leaving their default tolerogenic program apparently unaffected. This is consistent with the view that IL-6 cannot down-regulate the expression of IFN-inducible genes, and possibly IDO, in cells lacking SOCS3 (3).

View larger version (37K): [in this window] [in a new window]   FIGURE 2. Effects of specific SOCS3 gene silencing on CD8+ DC function. A, RT-PCR analysis of SOCS3 expression in CD8+ DCs treated with SOCS3-specific siRNA. Control cells were treated with negative control siRNA or DOTAP alone. SOCS1 gene expression was also assayed as a specificity control. B, The effects of CD28-Ig and IL-6 on CD8+ DCs require SOCS3. P815AB-pulsed CD8– DCs or a mixture of CD8– DCs and 3% CD8+ DCs were transferred into recipient mice to be assayed for skin test reactivity at 2 wk. The CD8+ DC fraction was used as such or after treatment with CD28-Ig or rIL-6, with or without concomitant SOCS3 gene silencing by siRNA. Control cells (CD8+) consisted of cells treated with DOTAP alone. *, p < 0.001, experimental vs control footpads.

Apart from the effects of IL-6 on CD8⁺ DCs, the cytokine can directly reinforce the basal immunogenic activity of CD8^– DCs when these cells are treated with rIL-6 and then admixed with untreated CD8⁺ DCs, thus enabling the development of P815AB-specific skin test reactivity (14). However, this effect is lost when the CD8⁺ DC fraction is treated with CTLA-4-Ig before peptide loading and mixing with CD8^– DCs (15). We compared the effects of CTLA-4-Ig and CD28-Ig on untreated and siRNA-SOCS3-treated CD8⁺ DCs, respectively, when these cells were cotransferred with CD8^– DCs activated by IL-6. We assayed the development of P815AB-specific reactivity in hosts transferred with IL-6-treated CD8^– DCs, either alone or in combination with 3% cells of the other subset, treated with CTLA-4-Ig, CD28-Ig or rIL-6, with or without SOCS3 siRNA (Fig. 3). In line with previous results, CTLA-4-Ig-treated CD8⁺ DCs were found to inhibit priming by IL-6-conditioned cells of the other subset (9, 15). Remarkably, the same pattern of reactivity was displayed by CD8⁺ DCs exposed to CD28-Ig or IL-6 in the presence of SOCS3 siRNA. Also, the effect of CTLA-4-Ig on CD8⁺ DCs as well as that of CD28-Ig on SOCS3-deficient CD8⁺ cells was due to active suppression involving IDO because it could be reversed by the addition of the enzyme inhibitor 1-MT during cell exposure to CD28-Ig (Fig. 3). Thus, the functional effects of CD28-Ig on CD8⁺ DCs are remarkably similar to those of CTLA-4-Ig once SOCS3 expression has been silenced. It has been shown that IL-6 strongly activates STAT3 and induces the expression of IFN-responsive genes in SOCS3-deficient macrophages, indicating that IL-6 might mimic the actions of IFNs (4, 5). Although it is possible that lack of SOCS3 enables efficient IFN- signaling in DCs treated with CD28-Ig, IL-6 might also induce IFN--like responses, including activation of IDO, in DCs lacking SOCS3.

View larger version (22K): [in this window] [in a new window]   FIGURE 3. CD28-Ig and IL-6 become immunosuppressive in DCs lacking SOCS3. The priming ability of otherwise immunogenic, IL-6-conditioned CD8– DCs was assayed in the presence of a minority fraction (3%) of CD8+ DCs treated with CTLA-4-Ig or exposed to CD28-Ig or rIL-6, with or without concomitant SOCS3 gene silencing by siRNA. The effect of CTLA-4-Ig on CD8+ DCs and that of CD28-Ig on SOCS3-deficient cells were also studied in the presence of 1-MT treatment. Control cells were treated with negative control siRNA. *, p < 0.001, experimental vs control footpads.

To ascertain whether IL-6 will induce an IFN-like response through STAT proteins in DCs lacking SOCS3, we assayed the cytokine for possible direct effects on the induction of immunosuppressive tryptophan catabolism. STAT1 phosphorylation is normally required for IFN--induced transcription of the Indo gene (8, 17, 18). However, prolonged STAT3 activation is observed in response to IL-6 in cells lacking SOCS3, and STAT3 may be involved in the activation of IFN-inducible genes by IL-6 (7). We measured STAT1 and STAT3 phosphorylation in response to IL-6, IDO expression by immunoblot analysis, and tryptophan conversion to kynurenine in siRNA-SOCS3-treated and control CD8⁺ DCs. Limited STAT1 phosphorylation was observed in response to IL-6 in control cells, and the extent of phosphorylation was not enhanced by the absence of SOCS3 (Fig. 4A) and was not modified by the addition of anti-IFN- mAb (data not shown). In contrast, the amount of STAT3 phosphorylation was considerably higher in response to IL-6 in cells lacking SOCS3 (Fig. 4A). On analyzing IDO expression by Western blot using rabbit polyclonal IDO-specific Ab, we found that considerable expression of the enzyme protein was induced by IL-6 in cells lacking SOCS3 (Fig. 4B). This was reflected by enhanced conversion of tryptophan to kynurenine, an occurrence unaffected by the presence of IFN--neutralizing mAb (Fig. 4C). Therefore, IL-6 strongly activates STAT3 and tryptophan catabolism in DCs with silenced expression of SOCS3. IDO induction in DCs by IL-10 has been described previously to concur with enhanced STAT3 phosphorylation (24).

View larger version (48K): [in this window] [in a new window]   FIGURE 4. Modulation of SOCS3 by gene silencing or fusion proteins. A–C, siRNA enhances STAT3 phosphorylation, IDO expression, and tryptophan catabolism in response to IL-6. CD8+ DCs, either with control treatment (C) or subjected to siRNA treatment, were exposed to IL-6 and assayed for STAT1/STAT3 phosphorylation (A, 10-min exposure), as well as for expression of IDO protein (B, overnight exposure), by Western blot analyses. C, IL-6 was studied for the ability to induce tryptophan conversion to kynurenine in CD8+ DCs with or without concomitant SOCS3 gene silencing by siRNA, in the presence or absence of anti-IFN- mAb. Kynurenine levels in supernatants were measured by HPLC, and the results are the mean ± SD of triplicate samples in one of three experiments. Control treatment (C) consisted of DOTAP alone. D, RT-PCR analysis of SOCS3 expression in CD8+ DCs treated with CD28-Ig or CTLA-4-Ig for 2 h. Control treatment consisted of Ig-C3.

In DCs lacking SOCS3, the IFN-like actions of IL-6 are an important mechanism of CD28-Ig activity

The data reported so far suggest that in DCs treated with CD28-Ig in the absence of SOCS3, IFN- signaling may be released from a critical inhibitory control and that IL-6 might contribute to IDO activation through the induction of IFN--like responses. To ascertain the relative contributions of IFN- and IL-6 to the effects of CD28-Ig on CD8⁺ DCs lacking SOCS3, we adopted an experimental design similar to that of Fig. 3 and exposed siRNA-SOCS3-treated CD8⁺ DCs to CD28-Ig in the presence of Abs to IFN- or IL-6/IL-6R. The cells were then assayed for ability to block host priming to P815AB by IL-6-conditioned CD8^– DCs (Fig. 5). The results showed that neutralization of IFN- and blockade of IL-6 activity were each capable of negating the induction of a tolerogenic phenotype by CD28-Ig in DCs lacking SOCS3. Therefore, the IDO-activating, IFN--like responses induced by IL-6 in vitro in SOCS3-deficient DCs are reflected by effects in vivo that contribute critically to the tolerogenic properties of CD28-Ig in this specific setting.

View larger version (16K): [in this window] [in a new window]   FIGURE 5. Both IFN- and IL-6 contribute to the immunosuppressive effects of CD28-Ig acting on SOCS3-deficient DCs. The priming ability of IL-6-conditioned CD8– DCs was assayed in the presence of 3% siRNA-SOCS3-treated CD8+ DCs exposed to CD28-Ig with or without Abs to IFN- or IL-6/IL-6R. P815AB-specific skin test reactivity was measured at 2 wk. Control cells (CD8+) were treated with negative control siRNA. *, p < 0.001, experimental vs control footpads.

	Disclosures

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The authors have no financial conflict of interest.

	Footnotes

 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ This work was supported by a grant from the Italian Association for Cancer Research (to P.P.).

² Address correspondence and reprint requests to Dr. Paolo Puccetti, Department of Experimental Medicine, Via del Giochetto, 06126 Perugia, Italy. E-mail address: plopcc{at}tin.it

³ Abbreviations used in this paper: SOCS, suppressor of cytokine signaling; DC, dendritic cell; siRNA, small interfering RNA; DOTAP, 1,2-dioleoyl-3-trimethylammonium propane; 1-MT, 1-methyl-DL-tryptophan.

Received for publication February 9, 2005. Accepted for publication March 31, 2005.

	References

Top Abstract Introduction Materials and Methods Results and Discussion Disclosures References

 

1. Alexander, W. S., D. J. Hilton. 2004. The role of suppressors of cytokine signaling (SOCS) proteins in regulation of the immune response. Annu. Rev. Immunol. 22: 503-529.[Medline]
2. Heinrich, P. C., I. Behrmann, S. Haan, H. M. Hermanns, G. Muller-Newen, F. Schaper. 2003. Principles of interleukin (IL)-6-type cytokine signalling and its regulation. Biochem. J. 374:(Pt. 1): 1-20.[Medline]
3. Stoiber, D., P. Kovarik, S. Cohney, J. A. Johnston, P. Steinlein, T. Decker. 1999. Lipopolysaccharide induces in macrophages the synthesis of the suppressor of cytokine signaling 3 and suppresses signal transduction in response to the activating factor IFN-. J. Immunol. 163: 2640-2647.[Abstract/Free Full Text]
4. Croker, B. A., D. L. Krebs, J. G. Zhang, S. Wormald, T. A. Willson, E. G. Stanley, L. Robb, C. J. Greenhalgh, I. Forster, B. E. Clausen, et al 2003. SOCS3 negatively regulates IL-6 signaling in vivo. Nat. Immunol. 4: 540-545.[Medline]
5. Lang, R., A. L. Pauleau, E. Parganas, Y. Takahashi, J. Mages, J. N. Ihle, R. Rutschman, P. J. Murray. 2003. SOCS3 regulates the plasticity of gp130 signaling. Nat. Immunol. 4: 546-550.[Medline]
6. Yasukawa, H., M. Ohishi, H. Mori, M. Murakami, T. Chinen, D. Aki, T. Hanada, K. Takeda, S. Akira, M. Hoshijima, et al 2003. IL-6 induces an anti-inflammatory response in the absence of SOCS3 in macrophages. Nat. Immunol. 4: 551-556.[Medline]
7. Johnston, J. A., J. J. O’Shea. 2003. Matching SOCS with function. Nat. Immunol. 4: 507-509.[Medline]
8. Grohmann, U., C. Orabona, F. Fallarino, C. Vacca, F. Calcinaro, A. Falorni, P. Candeloro, M. L. Belladonna, R. Bianchi, M. C. Fioretti, P. Puccetti. 2002. CTLA-4-Ig regulates tryptophan catabolism in vivo. Nat. Immunol. 3: 1097-1101.[Medline]
9. Fallarino, F., U. Grohmann, K. W. Hwang, C. Orabona, C. Vacca, R. Bianchi, M. L. Belladonna, M. C. Fioretti, M. L. Alegre, P. Puccetti. 2003. Modulation of tryptophan catabolism by regulatory T cells. Nat. Immunol. 4: 1206-1212.[Medline]
10. Mellor, A. L., D. H. Munn. 2004. IDO expression by dendritic cells: tolerance and tryptophan catabolism. Nat. Rev. Immunol. 4: 762-774.[Medline]
11. Orabona, C., U. Grohmann, M. L. Belladonna, F. Fallarino, C. Vacca, R. Bianchi, S. Bozza, C. Volpi, B. L. Salomon, M. C. Fioretti, L. Romani, P. Puccetti. 2004. CD28 induces immunostimulatory signals in dendritic cells via CD80 and CD86. Nat. Immunol. 5: 1134-1142.[Medline]
12. Logue, E. C., W. C. Sha. 2004. CD28–B7 bidirectional signaling: a two-way street to activation. Nat. Immunol. 5: 1103-1105.[Medline]
13. Costa-Pereira, A. P., S. Tininini, B. Strobl, T. Alonzi, J. F. Schlaak, H. Is’harc, I. Gesualdo, S. J. Newman, I. M. Kerr, V. Poli. 2002. Mutational switch of an IL-6 response to an interferon--like response. Proc. Natl. Acad. Sci. USA 99: 8043-8047.[Abstract/Free Full Text]
14. Grohmann, U., F. Fallarino, R. Bianchi, M. L. Belladonna, C. Vacca, C. Orabona, C. Uyttenhove, M. C. Fioretti, P. Puccetti. 2001. IL-6 inhibits the tolerogenic function of CD8⁺ dendritic cells expressing indoleamine 2,3-dioxygenase. J. Immunol. 167: 708-714.[Abstract/Free Full Text]
15. Grohmann, U., R. Bianchi, C. Orabona, F. Fallarino, C. Vacca, A. Micheletti, M. C. Fioretti, P. Puccetti. 2003. Functional plasticity of dendritic cell subsets as mediated by CD40 versus B7 activation. J. Immunol. 171: 2581-2587.[Abstract/Free Full Text]
16. Fallarino, F., C. Asselin-Paturel, C. Vacca, R. Bianchi, S. Gizzi, M. C. Fioretti, G. Trinchieri, U. Grohmann, P. Puccetti. 2004. Murine plasmacytoid dendritic cells initiate the immunosuppressive pathway of tryptophan catabolism in response to CD200 receptor engagement. J. Immunol. 173: 3748-3754.[Abstract/Free Full Text]
17. Fallarino, F., R. Bianchi, C. Orabona, C. Vacca, M. L. Belladonna, M. C. Fioretti, D. V. Serreze, U. Grohmann, P. Puccetti. 2004. CTLA-4-Ig activates forkhead transcription factors and protects dendritic cells from oxidative stress in nonobese diabetic mice. J. Exp. Med. 200: 1051-1062.[Abstract/Free Full Text]
18. Grohmann, U., F. Fallarino, R. Bianchi, C. Orabona, C. Vacca, M. C. Fioretti, P. Puccetti. 2003. A defect in tryptophan catabolism impairs tolerance in nonobese diabetic mice. J. Exp. Med. 198: 153-160.[Abstract/Free Full Text]
19. Fallarino, F., U. Grohmann, R. Bianchi, C. Vacca, M. C. Fioretti, P. Puccetti. 2000. Th1 and Th2 cell clones to a poorly immunogenic tumor antigen initiate CD8⁺ T cell-dependent tumor eradication in vivo. J. Immunol. 165: 5495-5501.[Abstract/Free Full Text]
20. Grohmann, U., F. Fallarino, S. Silla, R. Bianchi, M. L. Belladonna, C. Vacca, A. Micheletti, M. C. Fioretti, P. Puccetti. 2001. CD40 ligation ablates the tolerogenic potential of lymphoid dendritic cells. J. Immunol. 166: 277-283.[Abstract/Free Full Text]
21. Mellor, A. L., B. Baban, P. Chandler, B. Marshall, K. Jhaver, A. Hansen, P. A. Koni, M. Iwashima, D. H. Munn. 2003. Cutting edge: induced indoleamine 2,3 dioxygenase expression in dendritic cell subsets suppresses T cell clonal expansion. J. Immunol. 171: 1652-1655.[Abstract/Free Full Text]
22. Grohmann, U., R. Bianchi, M. L. Belladonna, C. Vacca, S. Silla, E. Ayroldi, M. C. Fioretti, P. Puccetti. 1999. IL-12 acts selectively on CD8^– dendritic cells to enhance presentation of a tumor peptide in vivo. J. Immunol. 163: 3100-3105.[Abstract/Free Full Text]
23. Grohmann, U., R. Bianchi, M. L. Belladonna, S. Silla, F. Fallarino, M. C. Fioretti, P. Puccetti. 2000. IFN- inhibits presentation of a tumor/self peptide by CD8^– dendritic cells via potentiation of the CD8⁺ subset. J. Immunol. 165: 1357-1363.[Abstract/Free Full Text]
24. Raftery, M. J., D. Wieland, S. Gronewald, A. A. Kraus, T. Giese, G. Schonrich. 2004. Shaping phenotype, function, and survival of dendritic cells by cytomegalovirus-encoded IL-10. J. Immunol. 173: 3383-3391.[Abstract/Free Full Text]

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				C. Orabona, P. Puccetti, C. Vacca, S. Bicciato, A. Luchini, F. Fallarino, R. Bianchi, E. Velardi, K. Perruccio, A. Velardi, et al. Toward the identification of a tolerogenic signature in IDO-competent dendritic cells Blood, April 1, 2006; 107(7): 2846 - 2854. [Abstract] [Full Text] [PDF]

				T. Suzuki, F. Schirra, S. M. Richards, N. S. Treister, M. J. Lombardi, P. Rowley, R. V. Jensen, and D. A. Sullivan Estrogen's and Progesterone's Impact on Gene Expression in the Mouse Lacrimal Gland Invest. Ophthalmol. Vis. Sci., January 1, 2006; 47(1): 158 - 168. [Abstract] [Full Text] [PDF]

				S.-Y. Tseng, M. Liu, and M. L. Dustin CD80 Cytoplasmic Domain Controls Localization of CD28, CTLA-4, and Protein Kinase C{theta} in the Immunological Synapse J. Immunol., December 15, 2005; 175(12): 7829 - 7836. [Abstract] [Full Text] [PDF]

				F. Fallarino, C. Orabona, C. Vacca, R. Bianchi, S. Gizzi, C. Asselin-Paturel, M. C. Fioretti, G. Trinchieri, U. Grohmann, and P. Puccetti Ligand and cytokine dependence of the immunosuppressive pathway of tryptophan catabolism in plasmacytoid dendritic cells Int. Immunol., November 1, 2005; 17(11): 1429 - 1438. [Abstract] [Full Text] [PDF]

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